1. Field of the Invention
The present invention relates to a material constituted of a silica shell containing a wax core, to the process for preparing the same, to the use thereof for the thermostimulated delivery of active substances, and also to the compositions containing such a material.
2. Description of Related Art
It may be useful to encapsulate molecules of interest such as medicaments, dyes, pigments, reactants, fragrances, pesticides, etc., in order to protect them from outside attacks, especially oxidation, in order to convey them to a site of administration where they will be able to be delivered or else in order to store them before use under conditions where they will be released from their capsule under the influence of an external stimulus. One of the first applications of microencapsulation was the development of a carbonless copy paper sold at the end of the 1960s in which microcapsules comprising an ink were present on the back of a sheet of paper so as to release the ink by rupture of the capsules under the pressure exerted by the tip of a pen when writing. These days, encapsulation is expanding in various industrial sectors such as the pharmaceutical, cosmetic, food, textile and agricultural industries. The capsules and microcapsules are becoming increasingly sophisticated, especially in the pharmaceutical field where they make it possible to carry out controlled and/or targeted delivery of active principles.
Various types and morphologies of capsules and microcapsules have already been proposed such as, for example, protein capsules, cyclodextrins, liposomes, concentrated lamellar vesicles, double emulsions, colloidosomes, microcapsules, silica nanocapsules and heat-sensitive polymers such as poly(N-isopropylacrylamide (PNIPAM), heat-sensitive hydrogel microspheres, microspheres of PNIPAM-polylactide, etc. Numerous methods that make it possible to prepare these various types of capsules and microcapsules have also been expanded and developed during recent years, such as, for example and nonexhaustively, the precipitation of polymers by phase separation, layer-by-layer electrolyte deposition, polymerization by interfacial polycondensation, etc.